Disinfectant effervescent tablet formulation

ABSTRACT

A water soluble effervescent tablet formulation for preparing a disinfecting solution comprising a first tablet containing a bromide releasing agent and a second tablet containing a hypochlorite releasing agent.

This is a continuation-in-part of application Ser. No. 08/539,873, filedOct. 6, 1995, U.S. Pat. No. 5,741,520.

FIELD OF THE INVENTION

The present invention relates generally to a method of cleaning dentaland medical instruments, equipment, and the like. More specifically, theinvention relates to an effervescent tablet formulation that can be usedto prepare a disinfecting solution useful for disinfecting inanimatesurfaces.

BACKGROUND OF THE INVENTION

In the medical and dental fields, walls, floors, examination chairs andtables, other equipment, and instruments used in examination andtreatment are contaminated by various organic materials which contain orsupport the growth of various microorganisms. Cleaning alone is notsufficient to kill or inhibit the growth of these organisms and use ofdisinfectants is necessary.

A disinfectant is a substance which destroys or irreversibly inactivatesinfectious or other undesirable bacteria, pathogenic fungi, and viruseson surfaces or inanimate objects. Disinfectants kill the growing formsbut not necessarily the resistant spore forms of microorganisms.Sterilizers, on the other hand, destroy the growing and spore forms ofviruses, bacteria, and fungi on inanimate surfaces. Sanitizers are usedto reduce the number of living bacteria or viable virus particles oninanimate surfaces, in water, or in the air, and fungicides andfungistats are used to inhibit the growth of or destroy fungi oninanimate surfaces.

It has become common practice to use glutaraldehyde solutions as surfacedisinfectants or sterilants in dental and medical facilities. However,while glutaraldehyde solutions are an effective disinfectant, there aremany drawbacks to the use of glutaraldehyde, including safety concerns,problems with storing the large volumes of solutions required, and thelimited shelf stability of solutions. In addition, if the glutaraldehydesolution is prepared by dilution of a concentrated solution there is theinconvenience of measuring and pouring the liquid concentrate.

The use of disinfectant or sterilant concentrates in a powdered form hasbeen taught in the prior art; for example, in U.S. Pat. No. 5,350,563 toKralovic et al. The problem with the use of powders as disinfectantconcentrates is that they also must be measured in order to prepare thediluted solution and must be poured from one container to another. Inaddition, there are sometimes problems with forcing the powder intosolution.

Another problem faced when using liquid or powdered concentrates is thatmany of the ingredients used for disinfectants can be harmful to humansand the handling of concentrated amounts of these ingredients can beeven more harmful. Care must be taken not to spill or come into contactwith any concentrate and not to inhale any dust from powderedconcentrates.

Other patents, for example, those of Hunt et al., U.S. Pat. No.4,265,847, and White et al., U.S. Pat. No. 4,536,389, teach effervescenttablets useful for preparing solutions for sterilizing or disinfecting.Such compositions are rapid water soluble tablets typically comprisingan active chemical compound, an alkali metal bicarbonate, e.g. sodium orpotassium bicarbonate, and a solid aliphatic carboxylic acid such ascitric acid, tartaric acid, adipic acid, or an acid salt thereof. Inuse, such tablets are dissolved in water whereupon the interaction ofthe bicarbonate and acid components results in the release of carbondioxide, thus increasing the rate of solution of the other componentsand producing a solution in which the active (disinfecting) ingredientis homogeneously dissolved. Methods for forming effervescent tablets arewell known in the art. For example, see U.S. Pat. No. 4,265,847 to Huntet al. and U.S. Pat. No. 5,114,647 to Levesque et al., which disclosuresare incorporated herein in their entireties, by reference.

Halogen compounds are effective as disinfecting agents but their use assuch agents is limited due to difficulties in storage, mixing, andhandling of concentrated halogens and instability of dilute forms. Theuse of sodium dichloroisocyanurate as a disinfecting agent is known inthe prior art. For example, see U.S. Pat. No. 4,536,389, to White etal., and U.S. Pat. No. 5,114,647, to Levesque et al.. Sodiumdichloroisocyanurate hydrolyses in water to produce hypochlorous acid(HOCl) and hypochlorite (OCl⁻), which exist in solution at anequilibrium that is dependent upon the pH of the solution. For example,as shown in FIG. 1, at neutral pH a solution consists of about 75%hypochlorous acid and 25% hypochlorite. The prior art teaches the use ofbromide as a disinfectant, the hypobromous acid and hypobromite speciesare produced in solution typically by the use of bromo,chloro-5,5-dimethylhydantoin. The hypohalous acid specie is theantimicrobial form of the above compounds, with the hypohalite havingsome antimicrobial effect. However, the negative charge of thehypohalite inhibits its diffusion through the cell wall ofmicroorganisms and thus lowers its antimicrobial effect.

Chloride and bromide have different equilibriums in solution, as shownby the chart of FIG. 1. The dissociation characteristics of hypobromousacid are such that the hypobromous acid is the predominant species overhypobromite up to a pH of about 8.3, which is the point when theconcentrations of hypobromous acid and hypobromite are about equivalent.However, hypochlorous acid is a predominant species over hypochloriteonly up until a pH of about 7.4. At a pH above about 6.0, as shown byFIG. 1, a solution of hypobromous acid is a much more effectivedisinfectant because more of the hypohalous species is present.Furthermore, in addition to the greater percentage of hypobromous acidcompared to hypobromite, hypobromous acid is a stronger antimicrobialagent than hypochlorous acid, as shown by FIG. 2.

Accordingly, there is a need for an effective disinfecting agentpackaged and supplied in a convenient effervescent form. Theeffervescent tablet must fully dissolve in a rapid fashion to form ahomogeneous disinfecting solution which is highly active and stable fora useful length of time.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an effervescenttablet formulation that can be used to prepare a disinfecting solutionwherein the formulation avoids the disadvantages and problems of priorart disinfectant concentrates.

It is an object of the present invention to provide a product to be usedfor preparing a solution for disinfecting dental and medical instrumentsand equipment that dissolves fully and results in a solution which hasdisinfecting power for a useful period of time over a wide pH range.

The present invention comprises a water soluble effervescent tabletformulation that can be added directly to water to prepare adisinfecting solution. The preferred disinfecting agent is a combinationof a bromide releasing agent and a hypochlorite releasing agent.Further, the formulation includes a stabilizer for increasing thestability of the effective disinfecting species in solution. Inparticular, a two tablet system has been developed wherein the bromidereleasing agent is in one effervescent tablet and the hypochloritereleasing agent is in a second effervescent tablet.

Sodium bromide is useful as the bromide releasing agent. Sodiumdichloroisocyanurate is useful to provide both hypochlorite and to actas a stabilizing agent to maintain desired levels of the activeingredients. Both tablets contain effervescent agents such as are usedin the art; for example, sodium bicarbonate in combination with citricacid. Other ingredients may optionally be included such as surfactants,deodorants, lubricants, and fillers.

The tablets prepared from the active agents and the effervescent agentsare of such a size and concentration to allow using whole tablets ormultiple tablets in a one quart volume or other typically used volume.The use of tablets eliminates having to dilute and mix concentrates, andstore diluted liquids. The use of tablets further eliminates having topour powder concentrates which may produce undesirable and harmful dust.The effervescence provides rapid solubility and mixing of the activeingredients. The use of the two tablet system allows for formation ofthe preferred hypobromous acid species.

Other objects, features, and advantages of the present invention willbecome apparent from the following detailed description in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the dissociation of hypobromous acid andhypochlorous acid.

FIG. 2 is a graph comparing the biocidal activities of hypobromous acidand hypochlorous acid.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is a two tablet effervescent tablet formulation.The tablets are made of appropriate sizes so that, preferably, one ofeach of the two tablets can be used for one quart of water. In this waya disinfecting solution can be made up as it is needed and does not needto made up in large quantities all at once. Therefore, storage problemsare avoided. The use of the effervescent tablets instead of aconcentrated liquid or concentrated powder allows for easy handling andmixing of the desired quantity of disinfecting solution.

One tablet, Tablet A, comprises a functional amount of effervescingagent and a bromide releasing agent. The preferred bromide releasingagent is sodium bromide (NaBr). However, other bromide releasing agentsmay be used, such as, for example, dibromo-dimethylhydantoin, chloro,bromo-dimethylhydantoin, and other bromide salts. The tablet furtherincludes lubricating agents such as, for example, sodium laurel sulfateand PEG 8000, and a filler such as sodium carbonate (soda ash). Tablet Bcomprises an effective amount of effervescing agent and a hypochloritereleasing agent such as sodium dichloroisocyanurate. It is anticipatedthat other hypochlorite generating agents can be used such as, forexample, lithium hypochlorite, calcium hypochlorite, magnesiumhypochlorite, and trichlorisocyanurate. Tablet B further can include afiller such as soda ash and lubricating agents such as sodium laurelsulfate and PEG 8000.

The two tablet formulation avoids reaction between bromide andhypochlorite which would occur if the two chemicals were packaged intoone effervescent tablet. The inventor has found that if a bromidereleasing agent and hypochlorite releasing agent are combined in asingle effervescent tablet, the chemicals will react if the tablet isexposed to a small amount of moisture. Thus, such tablets are notstable.

When one each of Tablets A and B are dissolved in water, sodiumdichloroisocyanurate hydrolyses into an equilibrium mix of hypochlorousacid and hypochlorite. Tablet B dissolves and renders free bromide (Br⁻)and NaBr. The hypochlorite oxidizes the Br⁻ so that hypobromite isformed. This species in turn forms hypobromous acid so that anequilibrium, dependent upon the pH, is achieved between hypobromite andhypobromous acid.

Effervescent tablet preparation is known in the art. A technique whichhas worked for the present invention is as follows. Effervescentgranules are prepared by mixing 200 kilogram batches of 52.5% sodiumbicarbonate, 41.5% citric acid, and 5.5% maltodextrin. This mixture ofsolids is combined with 20 liters of isopropanol and 800 milliliters ofdistilled water to form a very dry agglomeration. The agglomeration isdried and coarsely ground into effervescing granules. The effervescinggranules are mixed with the other ingredients of Tablet A and Tablet Bas described above. In one particular formulation the following amountsof ingredients were used.

    ______________________________________                                        Ingredient         Weight Percent                                             ______________________________________                                        TABLET A:                                                                     effervescent granules                                                                            66.0                                                       sodium bromide     10.0                                                       sodium lauryl sulfate                                                                             1.0                                                       soda ash           20.0                                                       PEG 8000            3.0                                                       Total =            100.0                                                      TABLET B:                                                                     effervescent granules                                                                            47.0                                                       sodium dichloroisocyanurate                                                                      24.0                                                       soda ash           25.0                                                       sodium lauryl sulfate                                                                             1.0                                                       PEG 8000            3.0                                                       Total =            100.0                                                      ______________________________________                                    

The above mixtures of ingredients were blended and then formed intotablets on an 18 station tablet press. Each tablet contained about 3grams.

One of each of the above tablets is added to about one quart of water atroom temperature and allowed to completely solubilize. The solution canbe applied to the area to be cleaned with a spray bottle, cloth, sponge,mop, or other cleaning method.

Another technique for effervescent tablet preparation which is usefulfor the present invention is as follows. The below listed ingredientswere blended and then formed into tablets on an 18 station tablet press.Each tablet contained about 3 grams. In this formulation effervescentgranules do not need to be prepared but rather the effervescing agentsare directly mixed with the other ingredients. This formula provides atighter and firmer tablet and is also less expensive.

    ______________________________________                                        Ingredient         Weight Percent                                             ______________________________________                                        TABLET A:                                                                     sodium bicarbonate 31.5                                                       citric acid        23.3                                                       soda ash           22.8                                                       sodium bromide     10.0                                                       sorbitol            7.4                                                       sodium lauryl sulfate                                                                             1.0                                                       carbowax 8000       3.0                                                       sodium benzoate     1.0                                                       Total =            100.0                                                      TABLET B:                                                                     sodium bicarbonate 25.0                                                       citric acid        18.3                                                       soda ash           21.7                                                       sodium dichloroisocyanurate                                                                      24.7                                                       sorbitol            5.3                                                       sodium lauryl sulfate                                                                             1.0                                                       carbowax 8000       3.0                                                       sodium benzoate     1.0                                                       Total =            100.0                                                      ______________________________________                                    

The weight percentages of the above ingredients can be altered and thetablet sizes can be altered as long as an effective pH and concentrationof halogen are present in the prepared solution. An effective pH for adisinfecting solution is from about 6.5-7.5. The pH of the solutionprepared as above is about 7.2. An effective concentration of halogen inthe prepared solution is from about 300-550 ppm. A preferredconcentration is from about 375-440 ppm. A solution prepared as abovehas about 400 ppm halogen.

It can be appreciated by those skilled in the art that a noveldisinfecting product and modifications thereof have been shown anddescribed in detail herein. Various additional changes and modificationsmay be made without departing from the scope of the present invention.

What is claimed is:
 1. An effervescent tablet formulation for preparinga disinfecting solution, comprising:a first tablet comprising aneffervescing agent, a bromide releasing agent, a lubricating agent and afiller; and a second tablet comprising an effervescing agent and ahypochlorite releasing agent.
 2. A tablet formulation for preparing adisinfecting solution, comprising:a first effervescing tablet comprisingan agent that releases bromide upon dissolution of the tablet in aqueoussolution; a second effervescing tablet comprising an agent that releaseshypochlorite upon dissolution of the tablet in aqueous solution; and alubricating agent in at least one of said first and second effervescingtablets.
 3. An effervescent tablet formulation for preparing adisinfecting solution, comprising:a first tablet comprising aneffervescing agent and a bromide releasing agent; and a second tabletcomprising an effervescing agent, a hypochlorite releasing agent, alubricating agent and a filler.
 4. The effervescent tablet formulationof claim 1, wherein said bromide releasing agent includes sodiumbromide.
 5. The effervescent tablet formulation of claim 1, wherein saidhypochlorite releasing agent is selected from the group consisting ofsodium dichloroisocyanurate, sodium trichloroisocyanurate, lithiumhypochlorite, calcium hypochlorite, and magnesium hypochlorite.
 6. Theeffervescent tablet formulation of claim 1, wherein said hypochloritereleasing agent includes sodium dichloroisocyanurate.
 7. Theeffervescent tablet formulation of claim 1, wherein said effervescentagent includes a mixture of sodium bicarbonate and citric acid.
 8. Aneffervescent tablet formulation for preparing a disinfecting solution,comprising:a first tablet comprising an effervescing agent and a bromidereleasing agent; and a second tablet comprising an effervescing agentand a hypochlorite releasing agent; wherein said effervescing agentincludes granules formed from a mixture of about 52.5% sodiumbicarbonate, about 44.5% citric acid, and about 5.5% maltodextrin, andin which wetting agents isopropanol and distilled water are used toagglomerate said mixture and the agglomerated mixture is formed intogranules.
 9. An effervescent tablet formulation for preparing adisinfecting solution, comprising:a first tablet comprising aneffervescing agent, a bromide releasing agent, a lubricating agent and afiller, said lubricating agent comprising a combination of sodium laurylsulfate and PEG 8000 and said filler comprising sodium carbonate; and asecond tablet comprising an effervescing agent and a hypochloritereleasing agent.
 10. The effervescent tablet formulation of claim 3,wherein said bromide releasing agent includes sodium bromide.
 11. Theeffervescent tablet formulation of claim 3, wherein said hypochloritereleasing agent is selected from the group consisting of sodiumdichloroisocyanurate, sodium trichloroisocyanurate, lithiumhypochlorite, calcium hypochlorite, and magnesium hypochlorite.
 12. Amethod for forming a disinfecting solution, comprising:preparing a firsteffervescent tablet comprising an effervescing agent and a bromidereleasing agent; preparing a second effervescent tablet comprising aneffervescing agent and a hypochlorite releasing agent; providing alubricating agent in at least one of said tablets; and dissolving atleast one of said first tablet and at least one of said second tablet inwater to form a disinfecting solution.
 13. The effervescent tabletformulation of claim 3, wherein said hypochlorite releasing agentincludes sodium dichloroisocyanurate.
 14. A disinfectant effervescenttablet formulation, comprising:a first tablet comprising an effervescingagent comprising a mixture of sodium bicarbonate and citric acid, afiller, sodium bromide, and a lubricating agent; and a second tabletcomprising an effervescing agent comprising a mixture of sodiumbicarbonate and citric acid, a filler, sodium dichloroisocyanurate, andlubricating agents.
 15. The effervescent tablet formulation of claim 3,wherein said effervescent agent includes a mixture of sodium bicarbonateand citric acid.